Anatomy of a Joint

Joints are the areas where two or more bones meet. Most joints are mobile, allowing the bones to move. Joints consist of the following:

Cartilage. A type of tissue that covers the surface of a bone at a joint. Cartilage helps reduce the friction of movement within a joint.

Synovial membrane. A tissue called the synovial membrane lines the joint and seals it into a joint capsule. The synovial membrane secretes synovial fluid (a clear, sticky fluid) around the joint to lubricate it.

Meniscus. This is a curved part of cartilage in the knees and other joints.

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What are the different types of joints?

There are many types of joints, including joints that do not move in adults, such as the suture joints in the skull. Joints that do not move are called fixed. Other joints may move a little, such as the vertebrae. Examples of mobile joints include the following: